\begin{tikzpicture}[>=Stealth]
    \draw (0,0) circle [x radius=1cm, y radius=1.6cm];
    \node at (0, 1.1) {正角};
    \node at (0, 0) {零角};
    \node at (0, -1) {负角};
    \node at (0, -1.9) {任意角的集合};

    \draw (3,0) circle [x radius=1cm, y radius=1.6cm];
    \node at (3, 1.1) {正实数};
    \node at (3, 0) {零};
    \node at (3, -1) {负实数};
    \node at (3, -1.9) {实数集 $R$};

    \draw [->] (0.5,1.1) -- (2.4,1.1);
    \draw [<-] (0.5,0.9) -- (2.4,0.9);
    \draw [->] (0.5,0.1) -- (2.4,0.1);
    \draw [<-] (0.5,-0.1) -- (2.4,-0.1);
    \draw [->] (0.5,-0.9) -- (2.4,-0.9);
    \draw [<-] (0.5,-1.1) -- (2.4,-1.1);
\end{tikzpicture}
